The present invention relates to a waterproofing apparatus for a terminal connecting portion of a sheathed wire being waterproofed by resin molding.
Generally, in a case of a sheathed wire, its front end is stripped to expose conductors therein, and stripped or bare conductors are connected to an electric part or to machinery through a terminal fitting which is crimped by such as caulking. Being left to be bare as it is after crimping, a water content goes into the sheathed wire owing to capillary phenomenon. For avoiding this, the terminal connecting portion including the bare conductors is protected by various covering means for waterproofing.
For example, a grounding terminal fitting described in Japanese Patent Publication No. 10-289745A is waterproofed by covering a thermally shrinkable tube on the bare conductors of the terminal connecting portion, and heating to deposit it thereon. Further, such a technique is obviously known as a connecting plate for battery holder set forth in Japanese Patent Publication No. 11-120986A, in which the terminal connecting portion is covered with a molding resin to provide the water proofing in wiring to an electric source of an electric vehicle, said terminal connecting portion being attached under pressure with a terminal fitting on a bare conductor.
FIG. 6 is for conceptually explaining the waterproofing apparatus of the latter related art, and is a sectional side view showing a structure of a molding die composing essential parts of the apparatus.
A molding die 1 comprises an upper mold 2 and a lower mold 3, which are provided at interiors with a molding part 4 being a molding cavity, and a molten molding resin shown with arrows 6 is inject to pour into said interior from a runner channel 5 of an injecting gate. At the interior of the mold 4, bare conductors 7a stripped by peering a front end part of the sheathed wire 7 are crimped with a terminal fitting 8 by caulking, and the thus formed terminal connection is set for positioning as a whole body excepting the only front end connecting portion of a terminal fitting 8.
The sheathed wire 7 does not require the waterproofing treatment at a part having length extending rearwards from the terminal fitting 8, and so this part should be projected outside of the die. With respect to this projecting part of the sheathed wire 7, for the molten molding resin 6 not to flow out therefrom, the molding part 4 is closed at one side with an elastic lid plate 9 such as a rubber material. The elastic lid plate 9 is of upper and lower division type composed of an upper part 9a and a lower part 9b, and the sheathed wire 7 of a part around said projection is elastically held vertically.
However, the elastic lid plate 9 serves to stop the molding resin 6 flowing out, and at the same time serves to hold the sheathed wire 7 to press it down, but being the rubber material, the following problems are present.
One of them is that when injecting to pour the molding resin 6, if a resin pouring force acts on the interior of the molding part 4, the elastic lid plate 9 is pressed from the inside due to the resin pouring force and is elastically deformed. Especially, as in FIG. 6, the elastic deformation is large on the upper part 9a of the plate 9, so that a part 9c of the plate 9 closely attaching the outer circumference of the sheathed wire 7 is pushed outside from the inside. As a result, a space is created between the parts 9a, 9b and the outer circumference of the wire, and the molding resin 6 inconveniently flows outside of the die.
Another problem results from difference in heat conductivity between the elastic lid plate 9 of the rubber material and the metal-made upper and lower molds 2, 3. That is, as the rubber material of the plate 9 is smaller in the heat conductivity than the metal-made molds, a part of the molding resin 6 contacting the plate 9 within the molding part 4 takes a longer time to be consumed for cooling and hardening than other parts therewithin, and this is delayed in releasing from the molds so much, taking a longer time and causing to lower productivity.
A further problem is, as apparently from FIG. 6, that one side (right side in the figure) of the molding part 4 is substantially perpendicular to the elastic lid plate 9, and a rear part of the terminal connecting portion covered thereat is naturally formed to be upright. Therefore, if the sheathed wire 7 is bent, peeling instantly starts at the rear part of the terminal connecting portion.
It is accordingly an object of the invention to provide a waterproofing apparatus for a terminal connecting portion of the sheathed wire effective to prevention of peeling a resin by improving a shape of a molding part as the molding cavity of the die which composes the essential parts of the apparatus so as to prevent leakage of the molding resin from the molding part, accelerating to cool and harden the molding resin for realizing to leave from the die at earlier period of time so as to improve productivity, and forming the rear part of the terminal connection to be a suitable shape after molding to cover the resin.
In order to achieve the above objects, according to the present invention, there is provided an apparatus for waterproofing a terminal connecting portion of a sheathed wire, in which a terminal fitting and a bare conductor of the sheathed wire are connected with each other, by molding with resin, the apparatus comprising:
an upper mold having an inner space which defines an upper part of a molding cavity in which the terminal connecting portion of the sheathed wire is accommodated and molten resin is injected therein;
a lower mold having an inner space which defines a lower part of the molding cavity;
an upper elastic lid member provided with the upper mold; and
a lower elastic lid member provided with the lower mold, the upper and lower lid member elastically holding the sheathed wire therebetween when the connecting portion thereof is accommodated in the molding cavity,
wherein the inner space of the upper mold and the inner space of the lower mold is respectively narrowed toward the upper lid member and the lower lid member such that the molding cavity in the vicinity of the connecting portion of the sheathed wire has a fusiform shape.
In the above configuration, since the resin pouring pressure may be low, the poured resin would not push the lid member from inside of the molding cavity. Therefore, since elastic deformation of the lid member can be suppressed, the molding resin can be prevented from getting out of the molding die.
Preferably, the narrowed portions of the upper and lower molds are provided with radiating fins in which a plurality of concave grooves and convex ribs are alternately arranged.
In the above configuration, since cooling at a portion near the elastic lid member is accelerated by the radiating fins, there can be solved a problem due to heat conductivity difference as described above.
Preferably, the most narrowed portions of the narrowed portions define an aperture having a diameter which is substantially as same as a diameter of the sheathed wire.
In the above configuration, since the thickness of the molded portion which contacts with the sheathed wire is made minimum, even if the sheathed wire is bent or flexed at that point, the peeling-off of the resin can be prevented.
According to the present invention, there is also provided a terminal connecting portion of a sheathed wire which is waterproofed by the waterproofing apparatus as described above. There can be provided a fusiform molded portion which covers and waterproofs the terminal connecting portion in which a terminal fitting and a bare conductor of the sheathed wire are connected with each other.
In the above configuration, even if the sheathed wire is bent or flexed at that point, the peeling-off of the resin can be prevented.